This invention is generally related to switching dc voltage regulators, and more particularly to techniques for distributing an output current of a buck-type switching regulator equally among two or more phases of the regulator.
A dc voltage regulator converts an input dc voltage to either a higher or a lower dc output voltage. Such voltage regulators allow an electronic system to support components that are powered by different supply voltages, which helps control power consumption in the overall system. One type of voltage regulator is a switching regulator that is often chosen due to its small size and greater power efficiency. In a buck-type switching regulator, a solid-state switch is rapidly closed and opened to transfer energy between an input power supply (which may be unregulated) and an inductive element such as a stand-alone inductor or part of a transformer. The inductive element in turn typically feeds a common node to which another energy storage or filter circuit, such as a bulk capacitor, is connected. The switching causes an unavoidable ripple in the output current and the output voltage at the common node. The capacitor helps reduce this ripple, in an effort to obtain an essentially dc voltage. Note that the switching is controlled in response to feedback from the common node, in a manner that yields a desired voltage at the common node.
In a multi-phase regulator, multiple phases are provided to increase the available output current of the switching regulator. Each phase may be viewed as having a switchable solid-state power circuit that feeds an inductive element which in turns feeds the common node. A controller is provided that is able to correctly time the activation and deactivation of each phase, i.e. the closing and opening of the solid state switch in each phase, relative to the others, so that the desired voltage appears at the common node.
To improve the efficiency and reliability of the multi-phase regulator, the average output current at the common node should be distributed or shared equally among all of the phases. One limited solution for equally distributing the output current is to measure the current in each phase, sum these measured currents to yield an estimate of the output current, divide this sum by the number of phases to get the desired current in each phase, and then adjust the activation/deactivation of each phase to counteract the difference between the measured current and the desired current in that phase. Such a technique, however, may be too costly to implement in certain consumer products such as desktop and portable computers and servers.